Deizisau (Swabian: Deizisao) is a town in the district of Esslingen in Baden-Württemberg in southern Germany. It belongs to the Stuttgart Region (until 1992 Region Mittlerer Neckar) and the Stuttgart Metropolitan Region. Deizisau is located between the towns of Plochingen and Esslingen am Neckar, about 20 kilometers southeast of Stuttgart, the capital of Baden-Württemberg. The river Neckar flows through this town.

Deizisau is located on the left hillside of the Neckar-valley shortly after the "Neckarknie" in Plochingen where the river changes direction from northeast to northwest. At the western border of Deizisau, the Körsch flows into the Neckar; in the east a part of the Plochinger Kopf above the river knee lies inside the boundary.

No other villages except for the small town Deizisau belong to the Deizisau municipality. Inside the boundary of the municipality lies the abandoned village Kersch.

Adjoining municipalities are in the north Altbach, in the northeast Plochingen, in the southeast Wernau, in the south Köngen, in the southwest Denkendorf and in the northwest Esslingen am Neckar.

When it was settled in the 8th century, the area belonged to the Lorsch Abbey an der Bergstraße. The settlement was mentioned for the first time as Dizinsowe in a deed of the monastery Sirnau in the year 1268. Back then there was the medieval castle Körschburg on the boundary of Deizisau. Their robber barons did attack the merchants on the trading road in the Neckar valley regularly. They were banished by Württemberg in 1292 and the castle was destroyed. The town itself belonged to the patrician family Bürgermeister from the free imperial city Esslingen since 1296 and did enter into the possession of the Esslinger Katharinenhospitals through purchase in the year 1411. The old church of Deizisau was broken down because of its unsafe condition in 1495. It was then replaced by today's Protestant church. Thereby the church tower which had been constructed as a fortified tower was taken over from the old church. In 1532 the Reformation was introduced in Deizisau through the Katharinenhospital.

In the second half of the 16. century Deizsau became posting house on the first continuously run post line in the Holy Roman Empire, which back then headed from Venice to Antwerp. The first namely known postmaster was in the year 1585 Carlin Taxis, who descended the postal entrepreneurial family Thurn und Taxis. Some of his descendants still live in Deizisau today which is why Taxis is one of the most common last names.

At the beginning of the 17th century it raged at first the black death, killing 31 people in 1608, then the mercenary arms of the Thirty Years' War. Had the town counted 275 inhabitants in 1618, only 140 people were alive in Deizisau at the end of the war. Even the posting house was lost again during this period.

Deizisau did belong to the domain of the free imperial city Esslingen since the Middle Ages. Because of the rearrangement of Germany by Napoleon as a consequence of the German mediatization it became württembergian. In the 19. century Deizisau was on the one hand spared from war destruction but instead, it suffered from severe famine. Only for a short time after the end of the Coalition Wars a worldwide climate disaster happened following the eruption of a volcano in Indonesia in 1816, the so-called Year Without a Summer. In Deizisau it rained for 75 days in a row, hail destroyed the fields and the little harvest left could partly only be brought in after Christmas. The consequence was one of the most severe famines in the history of Deizisau. More bad harvests followed in the years from 1852 to 1855. In total 135 citizens left the town in those four hunger years to emigrate to the United States. On a rise in the Rotfeld between Deizisau and Köngen the famines are still reminded of through the hunger lime planted in the year 1833.